It is known that the formation of tertiary mercaptans by reaction of hydrogen sulphide with isobutylene homopolymers is generally accompanied by secondary products, more particularly products of decomposition of the isobutylene homopolymer, giving both lower olefins and the corresponding mercaptans. Mention may be made in this respect of U.S. Pat. Nos. 2,101,096; 2,426,646; 2,435,545 and 3,166,498, where the formation of tert-butyl mercaptan is observed for triisobutylene as starting olefin. These patents are hereby incorporated by reference.
The same applies, although in a lesser degree, to the process described in French Pat. No. 2,531,426, which concerns the synthesis of mercaptans in the presence of a catalyst comprising a cation exchange resin. The patent is incorporated by reference. The patent recommends that the temperature be controlled between the strict limits of 45.degree. and 75.degree. C. or, better, between 50.degree. and 70.degree. C. This process gives excellent results and is particularly efficient for the production of tert-butyl mercaptan, of tert-nonyl mercaptan and of tert-dodecyl mercaptan from isobutylene, propylene trimer and propylene tetramer, respectively. However, for isobutylene homopolymers such as, for example, diisobutylene or triisobutylene, a significant formation of light byproducts is also observed. Their presence in the reaction products requires purification by distillation and results in a final loss of active material in relation to the desired output of the tertiary mercaptan.